1. Field of the Invention
The present invention relates to an organic light emitting display device and a method of fabricating the same and, more particularly, to an organic light emitting display device and a method of fabricating the same, which is capable of improving the degradation of unit pixel edges caused by an electric field between an anode and a cathode by increasing a gap between the anode and the cathode.
2. Description of the Related Art
As a highly advanced information-oriented society has arrived, a consumer's demand for obtaining information rapidly and correctly in hand is increasing. In order to meet this demand, the development of various display devices which are thin and light to be easily carried and has a high information processing rate, has been accelerated. A conventional cathode ray tube (CRT) has problems of heavy weight, large volume and high power consumption, and a liquid crystal display device (LCD) has problems of complex processes, narrow viewing angles, and technical limitations on contrast ratio and a large-screen display. An organic light emitting display device (hereinafter, referred to as “OLED”) capable of solving the problems is rapidly rising as the next generation display device.
Since the OLED is an emissive display device in which, when voltage is applied to an organic layer including an organic emission layer, electrons and holes are recombined in the emission layer to emit light, the OLED does not require a backlight unit unlike the LCD. As a result, the OLED has advantages of light weight and small thickness, simple processes, response speed nearly equal to the CRT, and low power consumption.
In general, the OLED is classified into a passive matrix type and an active matrix type depending on driving methods. The passive matrix OLED has advantages of simpler manufacturing processes since its display region is configured of simple matrix elements made of anodes and cathodes, however, its application is limited to low-resolution and small-sized displays due to problems of low resolution, high driving voltage, and lifetime reduction of the material. On the contrary, the active matrix OLED is advantageous to apply to high-resolution and large-sized displays since its display region includes thin film transistors in every pixel and uniform current is supplied to the respective pixels regardless of the number of the pixels of the OLED to thereby have stable brightness characteristics and reduced power consumption. For these reasons, the active matrix OLED is at the center of attention amongst the next generation display devices by virtue of its excellent performance and market potential.
This OLED is made of an organic layer including at least an emission layer between an anode and a cathode. The OLED may realize a full color display by depositing the emission layer with materials for representing three primary colors of red, green and blue, and then patterning them.
FIG. 1 is a plan view of a conventional OLED. A method of fabricating the conventional OLED will be described with reference to FIG. 1.
FIG. 1 is a plan view of the conventional OLED, one pixel of which includes red (R), green (G) and blue (B) unit pixels.
Referring to FIG. 1, a scan line 10 arranged in one direction, data lines 20 insulated from and crossing the scan line 10, and common power source-supply lines 30 insulated from and crossing the scan line 10, and arranged parallel to the data lines 20 are disposed in the pixel. A plurality of unit pixels, for example, the red (R), green (G) and blue (B) unit pixels are defined by the scan line 10, the data lines 20 and the common power source-supply lines 30.
Each unit pixel includes a switching thin film transistor (TFT) 40 for performing ON/OFF operation according to control of a signal applied through the scan line 10, a capacitor 60 for storing a data voltage applied to the switching TFT, a driving TFT 50 for supplying a current corresponding to the data voltage stored in the capacitor 60, and an organic light emitting diode 80 for performing emission operation in response to the current supplied from the driving TFT 50. The organic light emitting diode 80 includes a first electrode 70. The organic light emitting diode 80 is supplied through the driving TFT 50 with a driving current corresponding to the data voltage stored in the capacitor 60, and performs the emission operation corresponding to the supplied current.
FIG. 2 is a cross-sectional view taken along the line I-I′ in FIG. 1, which shows one unit pixel of the OLED.
A method of fabricating the OLED will be described with reference to FIG. 2 as follows. First, a buffer layer 110 may be formed on an insulating substrate 100. The TFT, which includes a semiconductor layer 125, a gate insulating layer 120, a gate electrode 135, an interlayer insulating layer 130 and source and drain electrodes 145, is then formed on the buffer layer 110 using a conventional method.
A passivation layer 140 is formed on substantially the entire surface of the interlayer insulating layer 130, a planarization layer 150 is formed on the passivation layer 140, and then a via hole 165 exposing a predetermined portion of one electrode of the source and drain electrodes 145 is formed.
A first electrode 160 being in contact with the exposed predetermined portion of one of the source and drain electrodes 145 through the via hole 165 is formed.
After forming a pixel-defining layer 170 that covers the first electrode 160 having an indented shape due to the via hole 165, an opening 195 for exposing a portion of the first electrode 160 is formed on the pixel-defining layer 170.
Further, after forming an organic layer 180 including at least an emission layer in the opening 195 and in contact with the first electrode 160 exposed in the opening 195, a second electrode 190 is formed on substantially the entire surface of the substrate including the organic layer 180 in the opening 195.
Since electric charges may readily be concentrated on an edge 161 of the first electrode, the influence of the electric field between the edge 161 of the first electrode and the second electrode may be maximized to apply excessive voltage to the organic layer, thereby accelerating deterioration of the organic layer. As a result, lifetime of the fabricated OLED may be reduced.